PURPOSE: The objective of this paper is to determine whether hypoxia induces interleukin-1 beta (IL-1β) expression of rat monocytes involving in PKCα/Raf-1/ MAPK/NF-δB pathway.
METHODS: Rat monocytes were subjected to 0, 1, 3, 6, 9, 12 and 24 h of hypoxia (3%O2, 5%CO2, 82%N2) with or without isoform-selective PKC inhibitors, Raf-1 inhibitor, MAPK inhibitor and NF-δB inhibitor respectively. PKC and Raf-1 activity were analyzed by PKC kit and Raf-1 kinase cascade assay kit. NF-δB binding activity was analyzed by electrophoretic mobility shift assay. IL-1β mRNA levels were determined by reverse transcription-polymerase chain reaction.
RESULTS: Hypoxia induced significantly IL-1β mRNA expression (p ?? 0.01-0.05) in rat monocytes by increased activities of PKC, Raf-1, MAPK and NF-δB. PKCα inhibitor, Safingol, blocked hypoxia-mediated IL-1β mRNA expression and the inhibitors of other PKC isoforms had no effect. The results suggest that only PKCα play a role in induction of IL-1β expression by hypoxia. In addition, it was the Raf-1 inhibitor, GW 5074, rather than Ras inhibitor, manumycin A, suppressed hypoxia-mediated IL-1β mRNA expression, indicating that the induction of IL-1β mRNA expression by hypoxia depends on Raf-1, but not Ras. Moreover, the MAPK and NF-δB inhibitors decreased hypoxia-mediated IL-1β mRNA expression. It confirms the critical roles of MAPK and NF-δB in IL-1β induction in rat monocytes exposed to hypoxia.
CONCLUSION: Taken together, these data suggest that hypoxia induces significantly IL-1β expression in rat monocytes involving in the coordinate activity of PKCα/Raf-1/MAPK/NF-δB signaling pathway.
CLINICAL IMPLICATIONS: Although further studies are required to precisely define the potential functional role of hypoxia-mediated IL-1β expression in ARDS, our studies contribute to an understanding of signal transduction during the activation of rat monocytes and releasing IL-1β by hypoxia. Data accumulating via connected studies should be helpful in the development of therapeutic methods for ARDS and MODS.
DISCLOSURE: Guoming Wu, None.